The early findings of this research were presented in eCAADe 2005 International Conference, Lisbon primarily to highlight the concept of High Dynamic Range Images (HDRI) when representing architectural spaces in the form of still images. An experiment had been carried out to compare the results between HDRI rendering and ‘conventional’ lighting simulation algorithms namely ray tracing and radiosity. The results were based on static and using the same exposure factors, when capturing HDRI. This project, funded by Intensification Research Priority Area (IRPA) grant continues to present and report HDRI results in a simulation environment. In this paper, we first briefly explain on the concept of real and fake HDRI. Then a comparison experiment is conducted to compare these two methods and discuss the impact and effectiveness of the illumination computation in architectural simulation environment. In order to carry out the experiment, a few models of the architectural scenes were developed. These models were then textured with real photos and manipulated with ‘shaders’, and further rendered using fake and real HDRI techniques. As for the fake HDRI, two methods were developed. The first was using an image as the ambient map and different exposures were created by increasing the value of Hue, V of HSV and saturation. The second involved a series of digital photos with the selection of the brightest and darkest area using Adobe Photoshop to establish the scale of luminosity. A few camera movements were triggered and position for ‘real-time’ rendering simulation. The result of the experiment has shown a significant improvement on the rendering time and quality of the rendering. Finally this paper suggests the selection criteria for choosing real and fake HDRI, and how each technique can be best utilized for architectural representations in a simulation environment.